Phosphorus-based ligands are ubiquitous in catalysis, finding use for a number of commerically important chemical transformations. Phosphorus-based ligands commonly encountered in catalysis include phosphines and phosphites. Monophosphine and monophosphite ligands are compounds which contain a single phosphorus atom which serves as a donor to a transition metal. Bisphosphine, bisphosphite, and bis(phosphorus) ligands in general, contain two phosphorus donor atoms and typically form cyclic chelate structures with transition metals.
Two industrially important catalytic reactions using phosphorus ligands of particular importance are olefin hydrocyanation and isomerization of branched nitrites to linear nitrites. Phosphite ligands are particularly good ligands for both reactions. The hydrocyanation of ethylenically unsaturated compounds using transition metal complexes with monodentate phosphite ligands is well documented in the prior art. See for example U.S. Pat. Nos. 3,496,215; 3,631,191; 3655,723; 3,766,237; and 5,543,536. Bidentate phosphite ligands have also been shown to be particularly useful ligands in the hydrocyanation of activated ethylenically unsaturated compounds. See for example, Baker, M. J., and Pringle, P. G., J. Chem. Soc., Chem. Commun., 1292, 1991; Baker et al., J. Chem. Soc., Chem. Commun., 803, 1991; WO 93,03839; U.S. Pat. Nos. 5,512,696; 5,723,641; 5,688,986.
Recovery of the ligand and catalyst is important for a successful process. Typical separation procedures to remove the product(s) from the catalyst and ligand involve extraction with an immiscible solvent or distillation. It is usually difficult to recover the catalyst and ligand quantitatively. For instance, distillation of a volatile product from a non-volatile catalyst results in thermal degradation of the catalyst. Similarly, extraction results in some loss of catalyst into the product phase. For extraction, one would like to be able to tune the solubility of the ligand and catalyst to disfavor solubility in the product phase. These ligands and metals are often very expensive and thus it is important to keep such losses to a minimum for a commercially viable process.
One method to solve the problem of catalyst and product separation is to attach the catalyst to an insoluble support. Examples of this approach have been previously described, and general references on this subject can be found in “Supported Metal Complexes”, D. Reidel Publishing, 1985, Acta Polymer., 1996, 47, 1; Comprehensive Organometallic Chemistry, Pergamon Press, 1982, Chapter 55; and Beller, M., Cornils, B., Frohning, C. D., Kohlpaintner, C. W., Journal of Molecular Catalysis A, 104, 1995, 17-85 and Macromol. Symp. 1994, 80, 241. Specifically, monophosphine and monophosphite ligands attached to solid supports are described in these references. Bisphospine ligands have also been attached to solid supports and used for catalysis, as described in for example U.S. Pat. No. 5,432,289; J. Mol. Catal. A, 1996, 112,217; and J. Chem. Soc., Chem. Commun., 1996, 653. The solid support in these prior art examples can be organic, e.g., a polymer resin, or inorganic in nature.
Polymer-supported multidentate phosphorus ligands may be prepared by a variety of methods known in the art. See U.S. Pat. Nos. 4,769,498 and 4,668,651 and published international applications WO 9303839 and WO 9906146 and EP 0864577 A2 and EP 0877029 A2. The prior art discloses side-chain polymers containing multidentate phosphorus ligands as pendant groups.
There is always a need to develop a composition that can be used as or in a catalyst with substantially reduced loss during a catalytic reaction or separation of product from the catalyst. An object of the present invention is, therefore, to provide such a composition and to provide processes for making and for using the composition.
An advantage of the invention composition is that varying the molecular weight and degree of branching can control the solubility of the composition. Another advantage of the invention is that the catalyst produced by the composition can be substantially recovered by filtration. Other objects and advantages of the present invention will become apparent as the invention is more fully disclosed below.